- Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; or abstinence) prior to study entry and for the duration of study participation; women should continue birth control for 23 weeks after stopping nivolumab, and men should continue birth control for 31 weeks after stopping nivolumab; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately; men treated or enrolled on this protocol must also agree to use adequate contraception prior to the study, for the duration of study participation, and 31 weeks after completion of nivolumab administration